Researchers from North China Electric Power University have developed a flexible perovskite quantum dot (PQD) solar cell through an alkali-augmented antisolvent hydrolysis (AAAH) strategy that reportedly improves the charge transport of the perovskite absorber.
Quantum dots are tiny particles of semiconductors that can carry a charge and can be made from various materials. They have been investigated as possible solar cell materials for a long time. Those based on perovskites have proved particularly attractive to researchers working in photovoltaics, having already demonstrated efficiencies beyond 16%.
The scientists explained that PDQs are particularly suitable for photovoltaic applications due to their tunable bandgap energy, high photoluminescence quantum yields (PLQY), defect tolerance, and chemical processability. “In particular, lead iodide PQDs, methylammonium (MA), or formamidinium (FA) are promising for next-generation solar cells due to their high light absorption coefficients and efficiencies closer to the ideal Shockley-Queisser theoretical value,” they further explained.
The AAAH strategy adopted for the cell construction consisted of using a layer-by-layer deposition of PQD solid films, with each layer rinsed using an antisolvent that effectively removes the pristine ligands from the PQD surface without damaging the perovskite core.
Conventional neat ester antisolvents used so far for this kind of operation were found to lead to the direct dissociation of dynamically bound pristine oleic acid (OA) ligands rather than replacing them with hydrolyzed shorter counterparts, which the academics said create “extensive” surface vacancy defects to harvest energy carriers.
The research group identified methyl benzoate (MeBz), which is an organic ester compound widely used in perfumery industries, as an antisolvent ensuring “adequate” ligand exchange without compromising the integrity of the perovskite absorber.
The cell was fabricated with a substrate made of indium tin oxide (ITO), an electron transport layer (ETL) made of tin oxide (SnO2), the PDQ absorber, a spiro-OMeTAD-based hole transport layer (HTL), and a gold (Au) electrode.
The device was tested under standard illumination conditions and was found to achieve a power conversion efficiency of 18.37%, with an undisclosed independent solar cell accreditation laboratory having certified an efficiency of 18.30%.
This result is described as a world record for PDQ solar cells. “To further validate the potential of the AAAH-based ligand exchange for large-area photovoltaic applications, we fabricated 1 cm² solar cells, which achieved a champion efficiency of 15.60%, highlighting the promising scalability of this strategy,” the team said, noting that the best-performing devices also achieved steady-state efficiency of 17.85% and an average efficiency of 17.68%.
“Charge carrier dynamics revealed that the high photovoltaic performance was attributed to the assembly of light-absorbing layers with fewer defects, homogeneous crystallographic orientations, minimal PQD agglomerations, and favorable energy level positions through the AAAH strategy, resulting in suppressed trap-assisted recombination and facilitated charge extraction within PQDSCs,” the researchers concluded.
The cell was described in the study “Enriching conductive capping by alkaline treatment of perovskite quantum dots towards certified 18.3%-efficient solar cells,” published in nature communications.
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